1. Field of the Invention
The present invention relates to a mechanical ignition sensor for sensing a state of a sudden deceleration of a vehicle and for operating a detonating member.
2. Description of the Related Art
At an air bag apparatus mounted to a vehicle, for example, a gas generator having a mechanical ignition sensor is disposed. When the vehicle suddenly decelerates, the sudden deceleration is detected by the mechanical ignition sensor and then the gas generator operates. Gas is generated instantaneously so that the air bag body within the air bag apparatus is unfolded within the vehicle.
The mechanical ignition sensor used in the air bag apparatus basically comprises an ignition pin which ignites a detonator, an inertial mass which is inertially moved by a large acceleration, and a trigger member which is interposed between the ignition pin and the inertial mass so as to prevent the ignition pin from moving. Further, the air bag apparatus comprises a safety device for preventing the operation of the mechanical ignition sensor when the sensor is assembled to the vehicle or the like.
The safety device includes a safety lever, which engages the trigger member and prevents the movement of the trigger member regardless of the movement of the inertial mass. When the safety lever engages the trigger member, movement of the trigger member is forcibly prevented as described above. Accordingly, even if external force is unnecessarily applied to the vehicle when the safety lever is assembled thereto, operation of the sensor is prevented.
In the conventional mechanical ignition sensor having the aforementioned structure, movement of the trigger member is forcibly prevented by the safety lever. However, the inertial mass itself is movable in the operating direction of the inertial force. Consequently, when the safety lever is released (i.e., when the inertial mass is movable), in a case in which the inertial mass is located at a position at which the trigger member is moved, a drawback arises in that the trigger member moves and the mechanical ignition sensor operates at the same time that the safety lever is released.